Charge coupled devices are well known for their use in light detection in imaging systems. Arrays of charge coupled devices (CCDs) have been utilized for scanning in a raster scan type of arrangement or in a two dimensional array for use in television scanning, for example. The limiting factor for the use of charge coupled devices in imaging system is its low level light detection capability. In order to fully utilize the capability of a charge coupled device, rather than prior art vacuum tube or other kinds of photodetectors, the device must be capable of low level light detection and amplification.
According to the present invention, a charge coupled device (CCD) amplifier is utilized for amplification of charge packets as small as 500 electrons into usable signals. The disclosed process contributes very little noise to the signal. The charge amplifier consists of two connecting electrodes, one designated as the detector and the other designated as the response, physically separated by any convenient distance on which an NMOS field effect transistor (FET) is attached. Also coupled to the FET transistor is another electrode designated as the amplifier gate. The charge amplifier structure is embedded in the silicon dioxide layer, with the detector, response, amlifier electrodes and the NMOS (FET) Transistor being located some convenient distance above the silicon-silicon dioxide interface on the same LSI chip surface and becomes an integral part of the LSI amplifier design.